1. Field of the Invention
The present invention relates generally to machines for handling sheets of flexible material and, more particularly, to an apparatus for successively feeding single or multiple sheet newspaper sections from a stack thereof to a delivery station or to an awaiting preopened newspaper for insertion into the newspaper.
2. Discussion of the Prior Art
A feeding system for delivering multiple sheet newspaper sections to a delivery station is disclosed in U.S. Pat. No. 3,658,319, issued to Glaser on Apr. 25, 1972. This known system employs a vacuum assembly to initially grip a marginal portion of a lowermost sheet or section and, without actually withdrawing the section, to bend the gripped portion and introduce the portion into a mechanical conveying unit for delivery to an awaiting newspaper section.
The vacuum system employed in the device illustrated in U.S. Pat. No. 3,658,319, actuates a gripper in timed response to the extension and retraction of the gripper into and out of contact with the lowermost sheet or section. A valve apparatus is provided in the device which provides the timing of the vacuum pressure to the gripper, and includes a control plate component which pivots relative to the gripper assembly between positions turning the vacuum pressure to the gripper on and off.
This construction is advantageous in that the valve is located immediately adjacent the gripper so that the vacuum pressure is quickly transmitted to the gripper upon opening of the valve, and in that the movement of the valve is carried out by the gripper assembly as the assembly moves between engagement and sheet-releasing positions. However, it would be desirable to improve upon the valve construction in order to reduce the amount of movement of the valve, and to increase the useful life of the valve while decreasing the size and cost thereof as well as the number of parts required.
In another known construction in which a feeder system employs a vacuum operated gripper assembly to introduce a sheet or section into a mechanical conveying unit for delivery to an awaiting newspaper section, the vacuum assembly includes a valve apparatus that is constructed as a separate unit from the gripper assembly and is mounted away from the gripper assembly. According to this known construction, the valve apparatus is operated independently of the gripper assembly and is connected to the gripper assembly by a conduit extending therebetween which must be evacuated each time the vacuum pressure is connected to the gripper assembly.
Several drawbacks exist with this conventional construction. For example, because the valve is remote from the gripper assembly, an increased volume of space must be evacuated each time the vacuum pressure is connected to the gripper assembly such that a delay occurs between the time at which the valve moves to the open position and the time at which suction is experienced at the gripper. In devices where feeding rates are below 10,000 operations per hour, such delays are not critical. However, where more than 15,000 operations per hour are to be carried out, such as in an apparatus constructed in accordance with the present invention, such delays become significant and adversely effect the ability of the gripper to feed the lowermost sheet or section.
Another drawback of the conventional construction in which a remote valve is used resides in the inability of such a remote valve to be operated directly by the movement of the gripper between an engagement and sheet-releasing position. This type of construction requires additional structure to control the timing of operation of the remote valve.